This invention relates to a self-levelling concrete enabling to eliminate completely vibrations and surface finishing, as well as to a method for making a structural part from the said concrete, whereas the manufactured parts can be vertical as well as horizontal.
The self-levelling concretes are very fluid concretes than can be placed and tightened under the alone effect of gravity without calling for any vibrations. The self-levelling concretes also produce after hardening a homogeneous end product, which has not undergone any segregation. A description of such concretes can be found in the bibliographic synthesis by Thierry SEDRAN published in Bull.-Labo. P. and Ch., 196, ref. 3889, March-April 1995. A comment of these concretes can also be found in the article by NAGATAKI,  less than  less than Concrete Technology in Japan greater than  greater than  (chapter 3), published in Concrete Under Severe Conditions: Environment and Loading (Volume 1), edited by. K. SAKAI, N. BANTHIA and O. E. GJORV, 1995.
The self-levelling concretes notably and advantageously produce materials of a quality not so dependent on the workers"" know-how and the quality concrete as well as better steel coating, reduce the implementation durations and the necessary labour during casting, and improve ergonomy.
However surface defects frequently appear, especially macrobubbling.
This invention relates to a self-levelling concrete enabling to obtain better quality facing, avoiding macrobubbling and not requiring any surface finishing.
The invention also relates to such a self-levelling concrete, providing good rheology handling, can be cheap, enables using any cement amongst a wide variety of cements and can be manufactured in a ready-mix concrete plant thanks to a few hours"" rheology handling.
The invention also relates to a method for making a structural part from a self-levelling concrete, easy to be implemented, not requiring any cranes, thus providing time to enhance productivity of the building yard and particularly suited for a self-levelling concrete exhibiting the previous qualities.
In the following, the value ranges are inclusive.
The invention applies to a self-levelling concrete of known composition, comprising in weight, for cubic meter of concrete:
about 350 to 600 kg/m3 of binder, of which 200 to 500 kg/m3 are cement,
about 170 to 250 kg/m3 of water,
about 0.5 to 4 kg m3 of various agents and additives (dry extracts), comprising at least one superplasticizer,
the cubic meter supplement, in weight, of granulates and solid particles of size smaller than or equal to 12 mm, preferably smaller than or equal to 8 mm.
According to the invention, the superplasticizer is a hydrosoluble or hydrodispersible organic compound, which comprises at least one amino-di-(alkylene phosphonic) group, optionally as a salt, and at least one polyoxyalkylated chain. More precisely, the superplasticizer is a compound (I) or a salt of said compound (I), wherein this compound has the formula.: 
in which:
R is a hydrogen atom or a saturated or unsaturated monovalent hydrocarbon group, comprising 1 to 18 carbon atoms and optionally one or several heteroatoms: R being preferably a hydrogen atom or a monovalent saturated or unsaturated hydrocarbon group comprising 1 to 4 carbon atoms, 50% to 100% of the Ri are ethylene, 0 to 50% of the optional other Ri are similar or different from one another and represent an alkylene such as ethylene, propylene, butylene, amylene, octylene or cyclohexene, or an arylene such as styrene or methylstyrene; whereby the Ri may include one or several heteroatoms,
Q is a hydrocarbon group comprising 2 to 18 carbon atoms and optionally one or several heteroatoms,
A is an alkylidene group comprising 1 to 3 carbon atoms, A representing preferably the methylene group,
The Rj are similar or different from another and can be selected from
the Axe2x80x94PO3H2 group, whereas A has the meaning mentioned above,
and the group 
B designating an alkylene group comprising 2 to 8 carbon atoms, B representing preferably ethylene or propylene, A having the above mentioned meaning,
 less than  less than n greater than  greater than  is a number ranging from 20 and 250,
 less than  less than r greater than  greater than  is the number of [Rxe2x80x94O(Rixe2x80x94O)n] groups of Rj,
 less than  less than q greater than  greater than  is the number of [Rxe2x80x94O(Rixe2x80x94O)n] groups of Q,
the sum  less than  less than r+q greater than  greater than  should not exceed 3
 less than  less than y greater than  greater than  is an integer equal to 1 or 2,
Q, N and the Rj may form together one or several rings, whereas this or these rings may also comprise one or several other heteroatoms.
The salts of the compounds (I) can be stoichiometric or not, mixed or not and consist of alkaline metals, alkaline-earth metals, amines or quaternary ammoniums.
The form of the compounds (I) may vary from liquid to solid, while passing through the wax phase.
The supplement to cement to make up the binder advantageously consists of ground high furnace slag, volatile ashes, filler, calcareous or siliceous or other puzzolanic elements.
The category of the superplasticizers of the self-levelling concrete according to the invention is known in itself generally as a fluidising component for aqueous suspensions of mineral particles and hydraulic binder pastes, and is disclosed in the document FR-A-2.696.736. Moreover, a method for preparing such a fluidising component is described in the document FR-A-2.689.895. However, the use of this fluidising component as a superplasticizer in a self-levelling concrete according to the invention is new. We refer notably to the document FR-A-2,696.736 for a detailed description of the category of the compounds (I) and of the salts of said compounds (I) used as superplasticizers the self-levelling concrete according to the invention.
The self-levelling concrete according to the invention exhibits surprising results, which provide decisive advantages:
a) it avoids macrobubbling while allowing the bubbles to float up to the surface and thus provides facings of very smooth surface and superior quality, not requiring any surface finishing at a later stage;
b) it practically exhibits neither segregation nor exudation phenomenon, which consequently enables to avoid the requirement to add a viscosity agent and thus provides cost savings and easier implementation;
c) the cement contained in the self-levelling concrete according to the invention can be selected from a very wide variety of cements without affecting the qualities of the concrete significantly;
d) the facing obtained is clear or becomes clear rapidly (for example after a week) in quite numerous cases, even in the presence of a large quantity of volatile ashes or of dark cement, which provides the facing with higher aesthetic quality;
e) the concrete exhibits good rheology handling, which may generally last 3 hours at least.
The self-levelling concrete according to the invention may also enable vibration-less implementation, practically no exudation, rapid implementation, good pumping capacity and very good vibration-less horizontal levelling property. The concrete can be prepared in a conventional ready-mix plant without modification of this ready-mix plant and can be delivered, ready for use, by mixer trucks to the building yard. If needed, fluidity of the concrete is adjusted by complementary addition of the superplasticizer on the building yard. Thus, the doses of each component of the concrete can thus be regular.
Fluidity of the concrete removes traditionally slumping and levelling operations with a rule or an equivalent means, as well as the floating operation for horizontal concrete works, providing the man of the art adheres to the normal implementation conditions. To obtain a plane and smooth horizontal surface, it suffices to apply slowly a finishing bar over the surface of the fresh product. Indeed, concrete is almost self-smoothing. Besides, maintaining this fluidity for a reasonable duration, from 2 to 4 hours and good setting and hardening kinetics of the concrete, enable people to tread upon the manufactured part as soon as the day following the pouring of the concrete.
During slump flow tests, this concrete enables obtaining a sagging value greater than 70 cm after fluidisation on the yard and notably, preferably, between 73 and 77 cm. An average 28-day strenght at least equal to some 30 Mpas can also be provided.
Concrete, once hardened, becomes a structural part with a good surface aspect, smooth and plane, without requiring any sanding for horizontal parts. In the case of vertical parts, this surface exhibits a thin facing texture, which can meet the characteristics listed in the reference DTU21 (Unified Technical Document).
To meet the requirements of the self-levelling concrete according to the invention, the superplasticizer such as defined previously exhibits advantageously the following characteristics, taken separately or in association with all their technically possible combinations:
R is a hydrogen atom,
R is a monovalent saturated or unsaturated hydrocarbon group comprising 1 to 4 carbon atoms,
the Ri groups are selected from ethylene and propylene,
Ri is mainly ethylene, whereas the number of ethylene units corresponding to Ri is sufficient in order to keep the hydrosoluble or hydrodispersible property of the compound (I),
Q is a hydrocarbon group comprising from 2 to 12 and preferably from 2 to 6 carbon atoms and represents preferably ethylene and/or propylene, whereas the latter are provided advantageously in an amount of 95 mole %, the supplement consisting of other monomers such as cyclohexene or n-hexene,
the alkylidene group A comprises from 1 to 3 carbon atoms,
A is the methylene group,
the Rj group is the group xe2x80x94CH2xe2x80x94PO3H2 optionally as a salt or the group xe2x80x94C2H4N (CH2xe2x80x94PO3H2)2 optionally as a salt or the group xe2x80x94C3H6N (CH2xe2x80x94PO3H2)2 optionally as a salt,
the salts of the compound (I) are sodium, calcium or diethanolamine salts,
 less than  less than n greater than  greater than  ranges from 20 to 250, preferably from 30 to 150 and more preferably from 50 to 100,
the sum  less than  less than r+q greater than  greater than  is smaller than 3 and preferably equal to 1,
 less than  less than y greater than  greater than  is equal to 1.
Although it is generally not necessary, the self-levelling concrete according to the invention may comprise one or several viscosity agents selected for example from ultrathin silicae or organic compounds such as polysaccharides with high molecular weight such as starches, Xanthan gum, Welan gum or cellulosic derivatives, at the ratio of about 0 to 1 kg/m3 (dry extract) of the composition.
Nevertheless, one of the advantages of the concrete according to the invention is to allow to avoid the use of viscosity agents, which are often costly and difficult to be applied.
Advantageously, the compound (I) used as a superplasticizer in the self-levelling concrete according to the invention comprises one or several characteristics listed below:
(i) at least 50% of the Ri are ethylene and the other optional Ri are propylene;
(ii) Rj is selected from the groups xe2x80x94CH2xe2x80x94PO3H2, xe2x80x94C2H4N (CH2xe2x80x94PO3H2)2 and xe2x80x94C3H6N (CH2xe2x80x94PO3H2)2, optionally as a salt.
Very good results have been obtained with a diphosphonated compound (I) in which Ri is ethylene, Rj is xe2x80x94CH2xe2x80x94PO3H2.  less than  less than n greater than  greater than  ranges from 30 to 150 (inclusive), preferably from 50 to 100 (inclusive), the sum  less than  less than r+q greater than  greater than  is equal to 1 and  less than  less than y greater than  greater than  is equal to 1.
A compound that has given very good results has the following formula (II): 
and the salts thereof.
Advantageously, the quantity of the superplasticizer (I) comprising at least one amino-di-(alkylene phosphonic) group and at least one polyoxyalkylated chain, in the self-levelling composition, ranges from 0.2 and 2% in dry weight, based on the cement weight, preferably from 0.3 to 0.8% in dry weight.
According to an alternative embodiment of the self-levelling concrete according to the invention, further to the superplasticizer (I) of the above mentioned formula (I), the composition should comprise at least one hydrosoluble or hydrodispersible superplasticizer (PCP), of polycarboxylic acid type and comprising polyether chains.
These superplasticizers (PCP), which are based on carboxylic vinyle monomers, and optionally, on sulfonated monomers, are well known and are notably described in the U.S. Pat. No. 5.714.017 and the EP-patent 0.612.702.
Preferably, it is provided to vary from 0.1 to 10, the weight ratio of the superplasticizer (I) on the superplasticizer (PCP).
The combination of the superplasticizers (I) and (PCP) enables preparing self-levelling concretes with the requested fluidity and reduced water contents. Moreover, while varying the proportion of superplasticizer (I) with respect to the superplasticizer (PCP), time-related fluidity handling of the cement self-levelling concrete compositions can be modulated.
Preferably, the superplasticizer (PCP) provided in the self-levelling concrete according to the invention comprises polyether chains of various lengths. Advantageously, the superplasticizer (PCP) provided in the self-levelling concrete according to the invention is such that the polyether chains comprise, in average, at least 50% oxyethylene units (percentage expressed on the total of oxyalkylene units of the superplasticizer PCP). Preferably still, the other oxyalkylene units are oxypropylene units.
Advantageously, the self-levelling concrete according to the invention comprises at least one antifoaming agent. The chemical nature of the antifoaming agent is not critical. Preferably, tributylphosphate is chosen. The quantity of antifoaming agent is generally comprised between 0.01 and 0.3% in weight, based on the cement weight.
Advantageously, the self-levelling concrete according to the invention comprises at least one thickener. As regards the thickeners that can be used in the self-levelling concrete object of this invention, mineral compounds can be mentioned such as sepiolite or ultrathin silicae, or organic compounds, such as cellulose derivatives or polysaccharides with high molecular weight, such as Xanthan gum or mixtures of two or more thickeners mentioned above. The quantity of thickener can range from 0.005% to 0.05% in dry weight based on the cement weight.
When an antifoaming agent and, optionally, a thickener are poured in the self-levelling concrete according to the invention these are supplied, advantageously, simultaneously with the superplasticizer (I) into this composition, using a uniform and stable premixture. Preferably, this premixture comprises mainly:
water,
at least one antifoaming agent, not hydrosoluble or hardly hydrosoluble;
at least one superplasticizer (I) complying with the formula (I) and, optionally, another superplasticizer (PCP) hydrosoluble or hydrodispersible,
at least one organic compound (O) comprising:
at least one primary, secondary or tertiary amino group, optionally neutralised, in whole or in part, by an organic or mineral Brxc3x6nsted acid; and
at least one alkyl or alkyl-aryl chain, linear or branched, saturated or unsaturated, comprising at least 8 carbon atoms, and optionally heteroatoms, selected from oxygen, sulphur or nitrogen;
at least one mineral stabiliser when the pH-acidity of the said premixture is greater than 7, such as clays and sepiolites;
optionally, an acid or a base to adjust the pH of the said mixture.
In this premixture:
by  less than  less than antifoaming agent greater than  greater than , not hydrosoluble or hardly hydrosoluble, should be understood an antifoaming agent, weakly or not soluble in aqueous media at room temperature (about 20xc2x0 C.) and at atmospheric pressure;
by  less than  less than uniform mixture greater than  greater than  should be understood a mixture which, left to set, may range from a limpid mixture (such as a microemulsion) to a troubled mixture (such as an oil in water emulsion). Sometimes, a thin film, generally foam, can be present at the surface of the uniform mixture.
The organic compound (O) is preferably selected from oleic amine, coco-nut oil amine, tallow amine and the derivatives of these amines, in particular the derivatives of these amines with an oxyethylene unit or a chain containing no more than 8 oxyethylene units.
The invention also relates to a method for making a vertical structural part by injecting a self-levelling concrete according to the invention into a framework. In this method, the concrete is pumped in fluid form using at least one immersion tube with an injection end at a lower level than the framework.
This method, particularly suited to the self-levelling concrete according to the invention, enables homogeneous filling of the framework and avoids cumbersome devices and calling for tedious handling.
Preferably, the diameter of the immersion tube ranges between 35 mm and 65 mm, and is advantageously equal to 50 mm.
According to a first preferred embodiment of this method, the immersion tube is inserted into the framework through an upper opening in the framework.
In a second embodiment of this method, the immersion tube goes through the framework at the lower level of the framework. The workers"" task is therefore made easier and they have direct access to insertion orifices, to the tube, notably for very reinforced shells or very thin posts.
The invention also relates to a method for making a horizontal structural part by injecting a self-levelling concrete according to the invention into a plane framework or on a particular ground. In this method, after injection, a smoothing bar is applied regularly over the surface of the concrete in order to ensure surface evenness of the part.
There is no need for using a ground finishing product.